1. Field of the Invention
The present invention relates to acrylonitrile solutions of maleimides, a method for the preparation thereof, and acrylonitrile based copolymers obtained by the use of the acrylonitrile solutions.
The maleimides represented by N-phenyl maleimide and the like are used as a heat resistance enhancer for such acrylonitrile based copolymers as acrylonitrile-butadiene-styrene (ABS) resin, acrylonitrile-acrylic rubber-styrene (AAS) resin, acrylonitrile-styrene (AS) resin, and acrylonitrile-chlorinated polyethylene-styrene (ACS) resin.
2. Description of the Prior Art
The maleimides which are in a solid state at room temperature have been heretofore handled generally in such forms as powder, flakes, and tablets. The maleimides in these solid forms, however, undergo gradual comminution and yield minute particles copiously during the course of transportation and consequently give rise to numerous problems such as deterioration of the work environment. For the solution of these problems, a method for enabling the maleimides to be handled securely in the form of acrylonitrile solutions obtained in advance by dissolving the maleimides together with a polymerization inhibition in acrylonitrile (JP-B-03-12,057) has been proposed. Since this method which permits the maleimides to be handled in the form of acrylonitrile solutions is excellent in having solved the problems mentioned above, it has been finding growing acceptance for industrial applications.
Since the acrylonitrile as the solvent for the acrylonitrile solutions of maleimides constitutes itself the source of the acrylonitrile component of the acrylonitrile based copolymers, the acrylonitrile solutions of maleimides, after being handled as for transportation, are used in their unmodified form for the production of the acrylonitrile based copolymers mentioned above.
The maleimides are yellow and the acrylonitrile solutions obtained by dissolving the maleimides in acrylonitrile are yellow and transparent. So long as the acrylonitrile solutions of maleimides are as yellow and transparent as they were when they were fresh from the production line, the acrylonitrile based copolymers as finished products using the solutions pose no particular problem concerning the color characteristics. In other words, the acrylonitrile based copolymers as the finished products cannot induce such coloration as tends to impair their marketability.
On no occasion, however, the acrylonitrile solutions of maleimides which are fresh from the production line are used immediately for the production of acrylonitrile based copolymers. Generally, the acrylonitrile solutions of maleimides after their production are transported by tank lorries and the like, stored in tanks and the like, or conveyed by the pipeline including pipe, valves, and nozzles (such as, for example, the polymer-feeding line from the storage tank for the acrylonitrile solutions of maleimides) before they are used for the production of acrylonitrile based copolymers. In the present invention, the transportation as by tank lorries, the storage as in tanks, and the conveyance as by the pipeline including pipe, valves, and nozzles (such as, for example, the polymer-feeding line from the storage tank for the acrylonitrile solutions of maleimides) will be referred to collectively as "handling."
After the acrylonitrile solutions of maleimides have been handled over a specific period, they possibly change color from the inherent yellow color to a brown color, for example, gain in the degree of yellowness (namely, darken the yellow color), or occasionally opacify. In this invention, these phenomena will be referred to collectively as "discoloration."
The acrylonitrile based copolymers obtained as finished products by using the acrylonitrile solutions of maleimides which have been discolored as described above are colored and have markedly impaired marketability. For the purpose of improving these finished products in marketability, the standards or demands imposed on the color of the acrylonitrile solutions of maleimides have been decisively gaining in exactitude in recent years. In the circumstances, such acrylonitrile solutions of maleimides as are appropriately used for the production of acrylonitrile based copolymers which sparingly incur discoloration due to aging during the course of handling, consequently preclude coloration, and excel in the color characteristics are strongly demanded.
Hereinafter, the acrylonitrile solutions of maleimides will be occasionally referred to simply as "acrylonitrile solutions."
An object of this invention, therefore, is to provide such acrylonitrile solutions of maleimides as are appropriately used for the production of acrylonitrile based copolymers which preclude coloration and excel in the color characteristics.
Another object of this invention is to provide a method for the production of the acrylonitrile solutions of maleimides mentioned above.
Yet another object of this invention is to provide acrylonitrile based copolymers of excellent color characteristics and high marketability which are obtained by using the acrylonitrile solutions of maleimides mentioned above.